System interconnect bus standards provide for communication between different elements on a chip, or different elements with a multi-chip module, a circuit board, a server node, or in some cases an entire server rack or a networked system. For example, the popular Peripheral Component Interconnect Express (PCIe or PCI Express) is a high-speed serial expansion bus providing interconnection between elements on a motherboard, and connecting to expansion cards. Improved system interconnect standards are needed for multi-processor systems, and especially systems in which multiple processors on different chips interconnect and share memory.
The interconnection of multi-processor computing resources and the associated memory poses several challenges. Generally, memory capacity requirements increase as the number of interconnected processors and accelerators increase. Furthermore, new interconnect standards may be incompatible with older standards, such as PCIe, and therefore render obsolete various system components and expansion devices which employ the older standards.
In the following description, the use of the same reference numerals in different drawings indicates similar or identical items. Unless otherwise noted, the word “coupled” and its associated verb forms include both direct connection and indirect electrical connection by means known in the art, and unless otherwise noted any description of direct connection implies alternate embodiments using suitable forms of indirect electrical connection as well.